GIANT MAGNETOSTRICTIVE MATERIALS - THIN-FILM FORMATION AND APPLICATION TO MAGNETIC SURFACE-ACOUSTIC-WAVE DEVICES

This paper points out current problems in the research and development of giant magnetostrictive materials (GMMs), and the use of thin film GMMs instead of bulk is emphasized because of the ready and inexpensiv e production and high applicability. One of the most prominent applica tions using GMM films is the magnetic surface acoustic wave device wit h tunability under an external magnetic field. Thin films of the giant magnetostrictive Tb0.3Dy0.7Fe2 alloy were prepared by vacuum flash ev aporation. The film structure was able to be changed from amorphous to crystalline by controlling the substrate temperature and deposition r ate. The crystalline films exhibited much higher magnetization and lar ger magnetostrictions than did the amorphous films. The contamination of the films in vacuum facilitated amorphization and markedly reduced the magnetostrictions of the films. X-ray diffraction and Auger electr on spectroscopy analyses revealed that the ratio of vacuum to depositi on rate is an appropriate indicator to assess the contamination effect of films.